Small-pitch micro-LEDs

Abstract

A micro-LED device and a method of fabricating the micro-LED device are disclosed. The method includes processing from a first side (e.g., p-side) of epitaxial layers of a micro-LED wafer to form individual mesa structures and a first solid metal bonding layer on the mesa structures, bonding a second solid metal bonding layer on a backplane wafer to the first solid metal bonding layer of the micro-LED wafer, removing the substrate of the micro-LED wafer and processing from a second side (e.g., n-side) of the epitaxial layers to isolate the solid metal bonding layers and form individual electrodes (e.g., anodes) for individual micro-LEDs, forming a dielectric material layer on surfaces in regions between the mesa structures, and depositing one or more metal materials in the regions between the mesa structures to form mesa sidewall reflectors and a common electrode for the micro-LEDs.

What is claimed is: 
     
       1. A micro-light emitting diode (micro-LED) device comprising:
 a backplane including pixel drive circuits and a plurality of metal contacts in a first dielectric material layer; 
 an array of micro-LEDs on the backplane, wherein each micro-LED of the array of micro-LEDs comprises:
 a metal electrode bonded to a metal contact of the plurality of metal contacts, wherein the metal contact has an area smaller than an area of the metal electrode and aligns with a region of the metal electrode; 
 a second dielectric layer on sidewalls of the metal electrode; 
 a back reflector on the metal electrode; 
 epitaxial layers on the back reflector and configured to emit visible light; and 
 a passivation layer on sidewalls of the back reflector and a portion of the epitaxial layers, 
 wherein an area of a first side of the epitaxial layers adjacent to the back reflector is equal to or less than the area of the metal electrode and is equal to or less than an area of a second side of the epitaxial layers opposing the first side; and 
 
 a common electrode between micro-LEDs of the array of micro-LEDs and coupled to sidewalls of the second side of the epitaxial layers in each micro-LED of the array of micro-LEDs. 
 
     
     
       2. The micro-LED device of  claim 1 , further comprising a partial reflector layer on the array of micro-LEDs, the partial reflector layer and the back reflector of each micro-LED of the array of micro-LEDs forming a resonant cavity for the visible light emitted in the epitaxial layers. 
     
     
       3. The micro-LED device of  claim 1 , wherein the back reflector includes:
 a distributed Bragg reflector including:
 a plurality of transparent oxide layers; and 
 a metal plug in the plurality of transparent oxide layers; and 
 
 a transparent current spreading layer between the epitaxial layers and the distributed Bragg reflector; and 
 a conductive material layer on the distributed Bragg reflector and opposing the transparent current spreading layer, 
 wherein the metal plug electrically couples the transparent current spreading layer to the conductive material layer, and 
 wherein an area of the back reflector is equal to the area of the first side of the epitaxial layers. 
 
     
     
       4. The micro-LED device of  claim 3 , wherein:
 a pitch of the array of micro-LEDs is less than 3 μm; and 
 
       a linear dimension of the metal plug is less than 20% of the pitch of the array of micro-LEDs.